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| author | Will Newton <will.newton@linaro.org> | 2014-03-13 09:45:29 +0000 |
|---|---|---|
| committer | Will Newton <will.newton@linaro.org> | 2014-04-17 11:40:36 +0100 |
| commit | 7c6776620db8e48fca492dbcac88d1c0f239dcde (patch) | |
| tree | 046a6f9a10d27442429c6c50b0e0f32fac286936 | |
| parent | e04a4e9d2e639a7770e1c0d24ecbcf92abf6bba8 (diff) | |
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manual/setjmp.texi: Clarify setcontext and signal handlers text
Calling setcontext from a signal handler can be done safely so
it is sufficient to note that it is not recommended.
Also mention in setcontext documentation that the behaviour of
setcontext when restoring a context created by a call to a signal
handler is unspecified.
2014-04-17 Will Newton <will.newton@linaro.org>
* manual/setjmp.texi (System V contexts): Add note that
calling setcontext on a context created by a call to a
signal handler is undefined. Update text to note that
setcontext from a signal handler is possible but not
recommended.
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | manual/setjmp.texi | 19 |
2 files changed, 17 insertions, 8 deletions
@@ -1,5 +1,11 @@ 2014-04-17 Will Newton <will.newton@linaro.org> + * manual/setjmp.texi (System V contexts): Add note that + calling setcontext on a context created by a call to a + signal handler is undefined. Update text to note that + setcontext from a signal handler is possible but not + recommended. + [BZ #16629] * stdlib/tst-setcontext.c: Include signal.h. (main): Check that the signal stack before and diff --git a/manual/setjmp.texi b/manual/setjmp.texi index 9446abcff7..ec79c26bb3 100644 --- a/manual/setjmp.texi +++ b/manual/setjmp.texi @@ -396,6 +396,9 @@ time of the call. If @code{uc_link} was a null pointer the application terminates normally with an exit status value of @code{EXIT_SUCCESS} (@pxref{Program Termination}). +If the context was created by a call to a signal handler or from any +other source then the behaviour of @code{setcontext} is unspecified. + Since the context contains information about the stack no two threads should use the same context at the same time. The result in most cases would be disastrous. @@ -483,11 +486,11 @@ and then resume where execution was stopped. This an example how the context functions can be used to implement co-routines or cooperative multi-threading. All that has to be done is to call every once in a while @code{swapcontext} to continue running a -different context. It is not allowed to do the context switching from -the signal handler directly since neither @code{setcontext} nor -@code{swapcontext} are functions which can be called from a signal -handler. But setting a variable in the signal handler and checking it -in the body of the functions which are executed is OK. Since -@code{swapcontext} is saving the current context it is possible to have -multiple different scheduling points in the code. Execution will always -resume where it was left. +different context. It is not recommended to do the context switching from +the signal handler directly since leaving the signal handler via +@code{setcontext} if the signal was delivered during code that was not +asynchronous signal safe could lead to problems. Setting a variable in +the signal handler and checking it in the body of the functions which +are executed is a safer approach. Since @code{swapcontext} is saving the +current context it is possible to have multiple different scheduling points +in the code. Execution will always resume where it was left. |